4556329 [rkeene@sledge /home/rkeene/devel/dact]$ cat -n comp_rle.c
  1 /*
  2  * Copyright (C) 2001, 2002, and 2003  Roy Keene
  3  *
  4  * This program is free software; you can redistribute it and/or
  5  * modify it under the terms of the GNU General Public License
  6  * as published by the Free Software Foundation; either version 2
  7  * of the License, or (at your option) any later version.
  8  *
  9  * This program is distributed in the hope that it will be useful,
 10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12  * GNU General Public License for more details.
 13  *
 14  * You should have received a copy of the GNU General Public License
 15  * along with this program; if not, write to the Free Software
 16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 17  *
 18  *      email: dact@rkeene.org
 19  */
 20 
 21 
 22 #include "dact.h"
 23 #include "comp_rle.h"
 24 #include <stdio.h>
 25 #ifdef HAVE_UNISTD_H
 26 #include <unistd.h>
 27 #endif
 28 #ifdef HAVE_STDLIB_H
 29 #include <stdlib.h>
 30 #endif
 31 
 32 
 33 /*
 34     mode        - DACT_MODE_COMPR or DACT_MODE_DECMP
 35                 Determine whether to compress or decompress.
 36     prev_block  - Previous (uncompressed) block.
 37     curr_block  - The data to be compressed.
 38     out_block   - Where to put data after compression.
 39     blk_size    - Size of prev_block and curr_block.
 40 */
 41 
 42 #if defined(AS_MODULE) && defined(USE_MODULES)
 43 #include "module.h"
 44 uint32_t DC_NUM=1;
 45 uint32_t DC_TYPE=DACT_MOD_TYPE_COMP;
 46 void *DC_ALGO=comp_rle_algo;
 47 char *DC_NAME="RLE Compression (MOD)";
 48 char *DC_SIGN="RGlnaXRhbFNpZ25hdHVyZQ==";
 49 char *DC_URL_GET="http://www.rkeene.org/projects/compression/dact/@@OSNM@@-@@ARCH@@/comp_rle.dll";
 50 char *DC_URL_VER="http://www.rkeene.org/projects/compression/dact/@@OSNM@@-@@ARCH@@/comp_rle.ver";
 51 uint32_t DC_VER=0x00080d;
 52 uint32_t DC_REQUIRE=DACT_MOD_REQ_ATLEAST|(0x00080d);
 53 #endif
 54 
 55 int comp_rle_algo(int mode, unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int
	bufsize) {
 56     switch(mode) {
 57         case DACT_MODE_COMPR:
 58             return(comp_rle_compress(prev_block, curr_block, out_block, blk_size, bufsize));
 59             break; /* Heh */
 60         case DACT_MODE_DECMP:
 61             return(comp_rle_decompress(prev_block, curr_block, out_block, blk_size, bufsize));
 62             break;
 63         default:
 64             printf("Unsupported mode: %i\n", mode);
 65             return(-1);
 66     }
 67 }
 68 
 69 int comp_rle_compress(unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int bufsize)
	{
 70     int i,x=0,m;
 71     unsigned char sentinel=0xff;
 72     unsigned char currchar=0, prevchar;
 73     unsigned char charcnt=0;
 74     unsigned int lowestcnt=0xffff;
 75     unsigned int count[256];
 76 
 77     for (i=0;i<256;i++) count[i]=0;
 78 
 79     for (i=0;i<blk_size;i++) count[curr_block[i]]++;
 80 
 81     for (i=0;i<256;i++) {
 82         if (count[i]<lowestcnt) {
 83             sentinel=i;
 84             lowestcnt=count[i];
 85         }
 86     }
 87 
 88     out_block[x++]=sentinel;
 89 
 90     prevchar=curr_block[0];
 91     for (i=0;i<(blk_size+1);i++) {
 92         if (i!=blk_size) { currchar=curr_block[i]; } else { currchar++; }
 93         if (prevchar!=currchar || charcnt==255 || i>=(blk_size)) {
 94             if (charcnt<=2 && prevchar!=sentinel) {
 95                 for (m=0;m<charcnt;m++) out_block[x++]=prevchar;
 96             } else {
 97                 out_block[x++]=sentinel;
 98                 out_block[x++]=prevchar;
 99                 out_block[x++]=charcnt;
100             }
101             charcnt=0;
102         }
103         charcnt++;
104         prevchar=currchar;
105     }
106     return(x);
107 }
108 
109 int comp_rle_decompress(unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int
	bufsize) {
110     int i,x=0,m;
111     unsigned char sentinel=curr_block[0];
112     unsigned char currchar;
113     unsigned char charcnt;
114 
115     for (i=1;i<blk_size;i++) {
116         currchar=curr_block[i];
117         if (currchar==sentinel) {
118             currchar=curr_block[++i];
119             charcnt=curr_block[++i];
120             if ((x+charcnt)>bufsize) {
121                 printf("Error in RLE compression!\n");
122                 return(0);
123             }
124             for (m=0;m<charcnt;m++) out_block[x++]=currchar;
125         } else {
126             out_block[x++]=currchar;
127         }
128     }
129     return(x);
130 }
4556330 [rkeene@sledge /home/rkeene/devel/dact]$

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last modified: 2004-04-04 07:01:50